Organizations such as on-line retailers, Internet service providers, search providers, financial institutions, universities, and other computing-intensive organizations often conduct computer operations from large scale computing facilities. Such computing facilities house and accommodate a large amount of server, network, and computer equipment to process, store, and exchange data as needed to carry out an organization's operations. Typically, a computer room of a computing facility includes many server racks. Each server rack, in turn, includes many servers and associated computer equipment.
Computer systems typically include a number of components that generate waste heat. Such components include printed circuit boards, mass storage devices, power supplies, and processors. For example, some computers with multiple processors may generate 250 watts of waste heat. Some known computer systems include a plurality of such larger, multiple-processor computers that are configured into rack-mounted components, and then are subsequently positioned within a rack system. Some known rack systems include 40 such rack-mounted components and such rack systems will therefore generate as much as 10 kilowatts of waste heat. Moreover, some known data centers include a plurality of such rack systems.
In some computer systems, a rack-level power distribution unit is provided in a rack to distribute electrical power to the many servers in the rack. The rack-level power distribution unit may include a large number of receptacles, each of which may be used to supply power to a different server. Rack-level power distribution units may be attached to one or both interior sides of the rack near one end of the rack. This mounting may place the receptacles of the power distribution unit in close proximity to the server power supplies. Such a mounting may, however, interfere with installation and removal of the server racks (for example, by obstructing the path of a server as it is slid into or out of the rack).
In one existing arrangement for a rack-based computer system, cooling air is introduced at the front end of a rack and into the front of servers mounted in the rack. Heated air is expelled through the rear of the server chassis and then exits through the rear of the rack. In many systems, electrical connections for power and data are at also located the rear of the rack system, along with associated equipment for the electrical connections such as rack-level power distribution units. With the electrical connections located at hot end of the rack, personnel may be forced to work in a hot environment to maintain the servers (for example, to connect and disconnect power and data cables). In addition, high temperatures at the rear of the rack may cause failures in the rack-level power distribution units (for example, due to thermal overload of breakers in the power distribution units).
A source of heat in many servers comes from on-board power supply units in the servers. Power supply units that are not properly cooled may be susceptible to failure. Many standard power supply units include an internal fan that draws air from inside the server chassis into the power supply case and then expels heated air to a location external to the server through a face panel in the power supply unit. This arrangement may be effective in cooling electrical components in the power supply unit. In some cases, however, the heat air expelled from the power supply unit may adversely affect cooling of other components in the server or in other parts of the system. For example, air expelled from a power supply unit may pre-heat air being introduced into a server chassis to cool critical components in the server, such as a central processing unit.
Some servers include a substantial number of hard disk drives (for example, eight or more hard disk drives) to provide adequate data storage. The hard disk drives include motors and electronic components that generate heat, which must be removed from the hard disk drives to maintain operation of the servers. This heat is sometimes removed by passing air over and on the sides the cases of the hard disk drives. In many existing servers, the hard disk drives are laterally spaced from one another to allow air to pass between adjacent hard disk drives to cool of the hard disk drives. Such lateral spacing may be needed to ensure adequate cooling of the hard disk drives, but also may have the effect of limiting the maximum density of the hard drives (that is, the number of hard disk drives that can be provided in a given amount of space in the server.)
Some data centers rely on DC-powered fans internal to servers to produce airflow through the servers in a rack system. Such fans may be, however, inefficient and prone to failure, and add to the costs and complexity of the servers. DC fans also require power conversion equipment (either internal or external to the servers) to supply the DC power for the fans.
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the invention to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. The headings used herein are for organizational purposes only and are not meant to be used to limit the scope of the description or the claims. As used throughout this application, the word “may” is used in a permissive sense (i.e., meaning having the potential to), rather than the mandatory sense (i.e., meaning must). Similarly, the words “include,” “including,” and “includes” mean including, but not limited to.